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Area unit population projections provide an indication of future changes in the size and age-sex structure of the population usually living in each area unit. You can use this information to see how particular areas will change in the future.

Area units are roughly the size of suburbs, but the 2,020 area units (boundaries at 1 January 2017) cover all of New Zealand and can be aggregated to meet your needs. The median size of area units is 2,000 people, while three-quarters of area units have a population between 100 and 4,000.

Users of projections range from planners to policy analysts, researchers to marketers. Government sector and community organisations use the projections to assess future needs for facilities and services such as housing, transport, schools, and recreation. Businesses can use the projections to analyse the potential market for new products and services, to site the location of new stores, and to develop strategic marketing initiatives.

More information

The updated 2013-base area unit population projections (released 2017), including projections by five-year age group and sex, are available from NZ.Stat.

An interactive map shows 'medium' population projections for area units. Click on an area unit to see projected population from 2013 (base) to 2043.

The updated 2013-base area unit population projections were released through 2017 on dates outlined below. These supersede the previous 2013-base area unit population projections.

What is the base population?

The area unit population projections have as a base the estimated resident population of each area at 30 June 2013. This population was based on the census usually resident population count of each area at 5 March 2013 with adjustments for:

net census undercount

residents temporarily overseas on census night

births, deaths, and net migration between census night (5 March 2013) and 30 June 2013

reconciliation with demographic estimates at ages 0–9 years.

The estimated and projected resident population is not directly comparable with the census usually resident population count because of these adjustments. For more information about the base population, refer to Information about the Population Estimates.

Alternative series are available

Three alternative projections (designated low, medium, and high) have been produced for each area unit using different fertility, mortality, and migration assumptions. Users can make their own judgement as to which projections are most suitable for their purposes. At the time of release, the medium projection is considered suitable for assessing future population change and is consistent with the median projection (50th percentile) of the National Population Projections: 2016(base)–2068 (released October 2016) and the medium projection of the Subnational Population Projections: 2013(base)–2043 update (released February 2017).

The low and high projections allow users to assess the impact on population size and structure resulting from lower growth and higher growth scenarios, respectively. The low projection uses low fertility, high mortality, and low net migration for each area. The high projection uses high fertility, low mortality, and high net migration for each area. The low and high projections are independent of the national and subnational population projections (regions, cities, and districts), as they represent plausible alternative scenarios for each area. As a result, low and high population projections at the area unit level do not necessarily sum to low and high population projections at broader geographic levels.

Nature of projections

The projections are designed to meet both short-term and long-term planning needs, but are not designed to be exact forecasts or to project specific annual variation. These projections are based on assumptions made about future fertility, mortality, migration patterns of the population. While the assumptions are formulated from an assessment of short-term and long-term demographic trends, there is no certainty that any of the assumptions will be realised. Therefore, the projections should be used as guidelines and an indication of the overall trend, rather than as exact forecasts.

While the projections take account of land planning and other government decisions known at the time the projections were made, Statistics NZ does not always have access to the policies or decisions of local and central government and businesses that assist in accurately forecasting small area populations. The projections do not take into account non-demographic factors (eg war, catastrophes, or major government and business decisions) which may invalidate the projections. The unpredictability of migration trends, especially in the short-term, can have a significant effect on projection results.

It is important to recognise that the projections simply reflect the assumptions made about future fertility, mortality, and migration trends. While the assumptions are formulated from assessment of short-term and long-term demographic trends, there is no certainty that any of the assumptions will be realised.

Method and assumptions

The 'cohort component' method was used to derive the population projections. Using this method, the base population is projected forward by calculating the effect of deaths and migration within each age-sex group (or cohort) according to the specified mortality and migration assumptions. New birth cohorts are added to the population by applying the specified fertility assumptions to the female population of childbearing age.

Projection assumptions are formulated after analysis of short-term and long-term historical trends, government policy, information provided by local planners (eg housing subdivisions, zoning changes) and other relevant information. The projections incorporate the latest demographic information available at the time of production, including birth and death registrations.

The assumed fertility and mortality rates are based on the registered births and deaths, respectively, for each area during the period 2012–16. The assumed rates are derived in a manner that ensures the projected number of births and deaths are consistent with those for higher geographic levels (ie medium fertility and mortality variants for each territorial authority area and New Zealand).

Migration at the subnational level has both an internal migration (to/from other areas of New Zealand) and an external migration (to/from overseas) component, although these separate components are difficult to quantify because of insufficient data. The assumed net migration for each area is based on observed net migration during each intercensal period from 1996 to 2013, estimated net migration between 2013 and 2016, the capacity of the area for further growth (for areas with net inflow), whether historical outflows can be sustained (for areas with net outflow), the desirability of the area to new migrants, and information available from and about local authority areas that relates to current and future developments and may affect population change.